Thirty monkeys were immunized with the following DNA vaccines composed of sequences representative of 2 macrophage-tropic molecular infectious clones, with 6 monkeys/vaccine 1) SIV/17E-Cl gene gun delivery 2) SIV/17E-Cl intramuscular injection 3) SIV/17E-Fr gene gun delivery 4) SIV/17E-Fr intramuscular injection 5) SIV/17E-Fr intrarectally Two to three booster immunizations using the same vaccine/route used in the primary dose have been given to each of these animals, with at least 2 month intervals between boosts. Class I restricted CTL activity has been measured 3 weeks after every boost in representative animals in each group. No detectable CTL activity against gag, pol, nef, or env has been identified in the PBMC of these animals. Immunizations will be continued until CTL activity is identified in the PBMC.